Surgical intervention at damaged or compromised bone sites has proven highly beneficial for patients, for example patients with back pain associated with vertebral damage.
Bones of the human skeletal system include mineralized tissue that can generally be categorized into two morphological groups: “cortical” bone and “cancellous” bone. Outer walls of all bones are composed of cortical bone, which has a dense, compact bone structure characterized by a microscopic porosity. Cancellous or “trabecular” bone forms the interior structure of bones. Cancellous bone is composed of a lattice of interconnected slender rods and plates known by the term “trabeculae.”
During certain bone procedures, cancellous bone is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine can be beneficially stabilized by the injection of an appropriate, curable material (e.g., polymethylmethacrylate (PMMA) or other bone curable material). In other procedures, percutaneous injection under computed tomography (CT) and/or fluoroscopic guidance of stabilization material into vertebral compression fractures by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Other skeletal bones (e.g., the femur) can be treated in a similar fashion. In any regard, bone in general, and cancellous bone in particular, can be strengthened and stabilized by a palliative injection of bone-compatible material.
Using a vertebropasty as a non-limiting example, a conventional technique for delivering the bone stabilizing material entails placing a cannula with an internal stylet into the desired injection site. The cannula and stylet are used in conjunction to pierce the cutaneous layers of a patient above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer cancellous bone underlying the cortical bone. Once positioned in the cancellous bone, the stylet is then removed leaving the cannula in the appropriate position for delivery of curable material to the trabecular space of the vertebra to reinforce and solidify the damaged hard tissue.
According to one method in the prior art, curable material, is introduced into an end of the cannula for delivery into the vertebra using a 1 cc syringe. A 1 cc syringe is used because it generates the high pressures required to the force curable material through the cannula and into the vertebra. A disadvantage of a 1 cc syringe is that an amount of curable material required for the procedure is larger than 1 cc. As a result, it is required to sterilely reload the syringe several times during the procedure. This increases time and complexity of the procedure and increases the risk of radiation exposure to the physician.
An improved prior art procedure uses a curable material injector loaded with a relatively larger volume of curable material. The injector is connected to an end of the cannula via a non-compliant supply tube. Pressure created at the injector pushes a column of curable material through the supply tube and into the cannula. Curable material is then delivered from the cannula into the trabecular space of the vertebra. Although an improvement over the use of a syringe, the method has several disadvantages.
The method results in less control for the physician because the flow of curable material through the cannula has been found to be somewhat unpredictable. A column of curable material is pushed by substantial pressure over a distance, creating a pressure head in the column. When the curable material column reaches the end of the cannula, physicians have experienced that the curable material can burst into the trabecular space, depositing an uncontrolled volume of curable material in an uncontrolled manner. Further, the transfer of curable material from the injector to the vertebra can only begin after the supply tube is connected to the cannula. A significant amount of time can elapse while the column of curable material is advanced through the supply tube and cannula.
Moreover, during a long procedure, curable material can begin to solidify inside of the cannula. After the desired amount of curable material is deposited in the vertebra, the cannula is removed at the completion of the procedure. The curable material that was in the cannula that may have begun to set may remain attached to the core of curable material in the bone. As the cannula is removed, the curable material may break inside of the cannula instead of at the tip of the cannula and leave a “spike” of curable material protruding from the vertebra.
There exists a need in the medical device field for an improved subcutaneous bone material delivery system. The present invention provides an efficient device and method of introducing curable material, or other material, into a bone structure in a controlled manner.